[texhax] font

Hi,
I am confused about how to pick up the right font to achieve the same
effect as the achemso style.
Here is the simple .tex files.
################################################################################3
$ more dark.tex
\NeedsTeXFormat{LaTeX2e}[1997/12/01]
\documentclass[%
a4paper,
journal=jacsat,
manuscript=article,
layout=traditional]{achemso}
\title{try}
\begin{document}
\section{dark one}
I wish to have this effect.
\end{document}
########################################################################
$ more light.tex
\NeedsTeXFormat{LaTeX2e}[1997/12/01]
\documentclass[a4paper]{report}
\usepackage{achemso}
\setkeys{acs}{usetitle = true}
%\usepackage{helvet}
%\renewcommand*\familydefault{\sfdefault} %% Only if the base font of
the docum
ent is to be sans serif
%\usepackage[T1]{fontenc}
\begin{document}
\section{light one}
This is my working one, need use documentclass \{report\}.
I wish the characters in this one can be as dark and clear as the
achemso one,
or similar good effect.
\end{document}
########################################################################
Thanks ahead for your suggestions,
Best regards,